Multi-Shot Injection Molding

Two Shot LSR Molding 

Multi-shot or multi-component injection molding is a collective term that refers to an injection molding process where two or more materials are molded in the same molding machine and within the same molding process. The result, an integrated molded component consisting of multiple materials and substrates.

In two shot molding, the LSR and thermoplastic parts are both molded and combined during the same molding cycle. The molds for the LSR and thermoplastic parts share the same platen in the molding machine. Typically the mold for the LSR parts is on the top and the thermoplastics mold is on the bottom.

In 2k LSR injection molding, there are two types of molds used: transfer molds and rotary molds. Using a transfer molding process, after the thermoplastic parts are molded, the molded parts are robotically removed from the mold and transferred up to the LSR mold for completion.


What Is Two-Shot Injection Molding?

Two-shot injection molding is also called “2k molding” or co-injection molding. To successfully perform liquid silicone rubber two-shot molding, a specially designed co-injection molding machine is needed, and a mold builder and molder that are skilled and experienced in LSR processing to ensure accurate alignment and precision placement.

Two-shot LSR injection molding involves molding an LSR material and a second polymer in the same molding process. The second material can be either a compatible thermoplastic material or a different grade of LSR (different durometer or pigment). The two materials are molded during the same process and combined to form one integrated two-material component. This process is a two-shot injection molding process.

2-Shot vs. Overmolding

Is Two-Shot Molding the Same as Overmolding?

The overmolding injection molding process is sometimes confused with or referred to as two-shot molding. Although similar because the finished component of both consist of a combination of two different materials or substrates, the manufacturing process and bonding is different. In the 2k molding process, the two materials are both chemically and physically integrated providing a superior bond compared to overmolding.

In the overmolding process, a finished molded component or a metal or other substrate is placed within the LSR mold during the LSR molding process. Once introduced, the mold closes and the LSR is molded around or over the presented substrate or component, integrating the two.

LSR Overmolding

What are the Benefits of Multi-Material Injection Molding?

Multi-injection molding offers numerous functional, aesthetic, and cost-saving benefits.

Product Design Flexibility

For product designers, the use of multiple materials in a single component allows for greater design flexibility to achieve complex part designs, desirable product features, and enhanced product performance.

Diverse Material Characteristics

When utilizing more than one material, the desirable characteristics from each of the materials can be realized – the rigidity of a thermoplastic or weight of a metal mass combined with the flexibility, sealing, or delicate features of an LSR.

Product Performance

Liquid silicone rubbers are widely chosen for sealing parts due to their excellent mechanical and chemical properties.

When employing a multi-shot strategy, the LSR seal is integrated into the part design.

In the case of connectors, covers, valves, and others components that use a seal, when produced as a multi-material component the product’s performance is enhanced. A superior chemical bond is achieved, the seal fits perfectly, remains in-place and eliminates seal rollover or displacement that can occur with loose seals added during a secondary assembly process.

2k Vac regulator diaphragm-min

There are several benefits that can be achieved by choosing a multi-shot process versus a single-material part followed by assembly, heat staking, ultrasonic welding or other secondary process used to mechanically combine two or more substrates.

  • Cost and Time Savings
    A finished product is designed with various components each with desired features and functions. By integrating these components and performing in a single manufacturing process, a significant savings can be attained – a savings in production costs for added assembly or other secondary operation equipment, labor costs for manual operations and material handling, and a time savings.
  • Efficiency and Quality
    The combination of fewer production steps and a cleaner, smoother transition of materials offers a more efficient manufacturing process. By reducing the number of operations and suppliers, supply chains are streamlined reducing the risk and opportunity for errors and thereby improving quality.
  • Optimization
    The LSR Multi-Shot technology allows for part weight and space optimization, complex designs, the integration of multiple materials, and multiple functions into one component.
    LSR 2-Shot injection molding is well suited for parts with tight tolerances and complicated geometries, as well as parts with wall thickness consistency requirements. In some instances, complex part designs incorporating multiple dual materials can only be achieved using two-shot process.

SIMTEC has perfected their multi-shot LSR injection molding technology and is one of few with the expertise and quality results needed for complicated, critical component requirements. We are proud to be able to provide our customers with solutions that meet the product performance they need for their long-term, high volume programs, and deliver quality precision multi-material components, consistently.

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Industries and Applications

Regardless of the industry, our liquid injection molding cells allow for the production of liquid silicone rubber parts or components that must withstand extreme conditions and make your products more effective. Industries and applications include:

Multi-Shot Injection Molded Part Applications

  • Handles for power tools
  • Medical/dental devices and products
  • Various multi-color parts and components
  • Any parts containing flexible/movable hinges
  • Products with soft-touch handles such as staplers
  • Two-tone plastic lenses
  • Caps
  • Enclosures
  • Parts containing seals
  • Flexible buttons
  • Automobile dashboards and instrumentation

SIMTEC: The Leader Among Multi-Injection Molding Companies

SIMTEC is proud to be a leader in the development of multi-injection molding technology. We’ve created and implemented technological approach to the integration of functions and materials, resulting in a proprietary multi-shot molding process that is unmatched in our industry.

Our advanced molds and molding capabilities enable us to fulfill even the most complex design requirements — without sacrificing quality, durability or aesthetic appeal. What’s more, we support our multi-shot injection process with a full complement of value-added services for our customers, such as design support and prototyping on the front end, and value-added inline secondary processes at the end for a full portfolio of services.

Contact us today to learn more about the many ways in which multi-injection molding can add value to your company’s manufacturing processes and applications.


Contact SIMTEC To Discuss Your Project Today

With design flexibility, advanced technology and exceptional quality, there’s no better partner to manufacture your high volume Liquid Silicone components than SIMTEC. Contact us today to discuss your requirements.

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